Mechanical connectors for joining members to transmit forces while providing for limited relative angular movement between the connected members are known. Such flex connectors, as they are commonly known, have been developed to carry either tension forces or loading, compressive loading or combinations of force loading between the two connected members. Such connectors have generally been designed as a compromise between permissible angular misalignment and force load carrying capacity. To increase the force load carrying capacity, efforts were also made to avoid combination loadings and subject the connection to only pure tension or compression force loading.
By limiting angular movement to pivoting movement about a single axis, a relatively large load carrying capacity could be maintained. However, such limited angular movement was unacceptable since most applications required a capability of universal, i.e. two axis, movement rather than a greater range of single axis angular compensation. Universal angular movement about a pair of intersecting perpendicular pivot axes normally requires a relatively complex connector structure for even a small angle of movement.
Frequently, such universal movement connectors have employed rubber or other resilient components to provide the desired angular flexibility for movement or alignment. While such an arrangement is satisfactory for many applications, such resilient components have inherent load carrying limitations even when formed in a metal/rubber laminate due to the rubber extrusion under continuous heavy force loading and rubber deterioration due to ageing. Accordingly, such components have not found widespread acceptance in connections subject to high force levels or where access for maintenance is restricted.
To eliminate load carrying rubber components, ball joints have been developed for providing metal-to-metal load carrying surfaces while providing for the desired universal angular movement. Such ball joint connectors have mating load carrying surfaces that are designed to slide on each other, but which slide surfaces are easily damaged. Sliding movement causes both wear and galling of these surfaces which requires frequent expensive repairs due to the high stress contact friction forces produced by the large forces. In addition, the large force moments necessary to produce the angular movement of the joint also require large side force loadings that may damage other structural components.
Such design and operating problems are often complicated by the additional requirement that the flexible connector also serve as an internal flow conductor for fluid under pressure. An example of such a fluid conductor application where the load carrying forces are great is in marine risers used in offshore drilling and production operations. In marine riser applications, the required primary load carrying capability is tension loading as other loading forces are controlled by other equipment. Another known application for large force load transfer or carrying connectors is tension legs on tension leg platforms which are also used in offshore operations to produce liquid hydrocarbons.